Answer A- The lac operon is activated when intracellular glucose levels are low. When the concentration of intracellular glucose is low, the levels of the signal molecule cAMP are high. More specifically the switch from glucose use to lactose use depends on the presence of both cAMP (Cyclic Adenosine Monophosphate) and a molecule called Catabolite Activator Protein(CAP). CAP binds with cAMP and the CAP-cAMP complex then binds to a specific DNA sequence found upstream of the lac operon operator and promoter. CAP-cAMP complex binding leads to enhanced RNA polymerase binding and activation of gene expression from the lac operon. Importantly, this process is affected by glucose levels, because cAMP levels are decreased in the presence of glucose catabolites. Thus, an elevation in cAMP concentration signals the absence of glucose, because lower glucose levels leads to increased cAMP levels. Inturn, increased cAMP levels lead to enhanced expression of the lac operon. In the presence of glucose, however, intracellular levels of cAMP fall, which leads to a lack of lac operon activation. The lac operon is therefore positively regulated by the absence of glucose.
help pleaseee In the lac operon, positive control occurs through the presence of the CAMP-CAP complex....
1) The lac operon is… a) Positive repressible b) Both negative inducible and positive repressible c) Positive inducible d) Negative inducible 2) An activator regulatory protein… a) Is involved in negative regulatory control b) Is a cis acting regulatory element c) Recruits RNA polymerase to the promoter d) Prevents RNA polymerase from binding the promoter 3) For the lac operon, the presence of the substrate (lactose) activates the repressor. True or False? a) true b) false 4) cAMP… a) Activates...
5. Briefly describe positive control in the lac operon when glucose is absent and lactose is present in high amounts.
In E coli the lac operon will express enzymes for the digestion of (Glucose/Lactose) when it is present, but if both the sugar mentioned before and (Glucose/ Lactose) are present the lac operon is repressed, resulting in the (Glucose/ Lactose) being used first. If there are high levels of cAMP, this means (Glucose/Lactose) levels are low, this results in a (Represser/Promoter) being activated and (Decreasing/Increasing) transcription of the lac operon.
3. The CAP activator protein and the Lac repressor both control the Lac operon (see Figure 28-14). Fill out the table below with No expression, Low/Medium expression, or High expression to summarize when the Lac operon will be expressed in each of the three E. coli strains in the table. An example has been done for you. RNA polymerase- binding site (promoter) CAP binding site start site for RNA synthesis operator Lacz gene -80 -40 14080 nucleotide pairs Figure 08-14...
5. Jacob, Monod, and Pardee used various E.coli mutants to help determine how the lac operon is regulated. The descriptions of some of the mutants are listed. For each E. coli mutant determine if the lac operon would be on or off in a lactose-only environment. laci mutant: This mutant produces a super repressor that is not inactivated by allolactose. It will still stick. Operater will be off, lacO mutant: This mutant has an altered operator sequence so that the...
26. The lac operon in E. coli consists of genes that code for enzymes necessary for the breakdown of lactose. When lactose is absent, the operon is inactive because a repressor protein binds to a specific site in the lac operon. When lactose is present, lactose molecules bind to the repressor protein, causing the repressor protein to dissociate from the binding site. In the absence of glucose (a preferred energy source for bacteria), the protein CAP binds to a regulatory...
1. If you isolated a mutation that disrupted a positive regulatory gene for the thr operon (which contains the genes needed to synthesize the amino acid threonine), what would the phenotype be? 2. Compare and contrast the positive regulation of expression of the lac operon by the cAMP-CAP complex with the negative regulation of expression of the lac operon by the LacI protein. You should have several similarities and parallel differences. 3. All human beings have a rich growth of...
The gene machine program shows you what happens when lactose is present in E. coli, and how the lac operon is under negative control. However, the lac operon is also under positive control from a protein called CRP, eAMP Receptor Protein. The absence of the lac repressor is essential but not sufficient for effective transcription of the lac operon. RNA polymerase also depends on the presence of CRP. Like the lac repressor, which can bind to the DNA and lactose....
A. Describe in detail the regulation of the prokaryotic lac operon for the following environment: Glucose is present, lactose present, & the repressor protein is mutated such that the allosteric site is non-functional and can no longer bind its substrate. Be sure to specify the presence or absence and location of Lac I, allolactose, cAMP, CAP, and RNA polymerase. B. Indicate whether transcription is occurring at a basal level, a high level, or not at all.
Imagine you are carrying out research on the lac
operon. You isolate six mutations in the lac operon by
measuring the amount of beta-galactosidase made in mutant cell line
under three different conditions: no lactose/no glucose; lactose
only; and lactose/glucose. Your results are shown in the table.
Strain
No Lactose, No Glucose
Lactose
Lactose, Glucose
Wild-type
None
High
Low
Mutant 1
None
None
None
Mutant 2
None
None
None
Mutant 3
None
Low
Low
Mutant 4
None
Low
Low
Mutant...